Power-transmission mechanism.



No. 854,749. PATENTED MAY 28, 1907. 0. MACMILLAN. 'POWERTRANSMISSION MECHANISM.

APPLICATION FILED DEC. 1, 1905.

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0. MACMILLAN. POWER TRANSMISSION MECHANISM.

' APPLICATION FILED DEO.1, 1905.

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UNITED STA'E S Ii A L1;ENT OFFICE.

CAMPBELL .MACMILLAN, OF SCIIENECTADY, NEW YORK, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

POWER-TRANSMISSION MECHANISM.

s ecification of Letters Patent.

Patented May 28, 1967.

Application filed'Decemher I, 1905. Serial No- 289,980.

chronousmotor to a load operating at varying speeds.

It has been proposed heretofore to employ a direct-current dynamo-electric ma chine of the commutator type as a slipping magnetic clutch between a constant speed drivingmember and a variable speed drive member.- With such an arrangement, commutation difliculties are likely to arise in large machines with suddenly varying loads or'speeds.

Since a unipolarmachine requires no commutator, commutat1on troubles do not arise.

Furthermore the revolving element of a unipolar machine ma small inertia, which is a great advantage in cases when frequent starts with rapid acceleration are required.

My invention in one aspect, accordingly, consists in employing a unipolar machine as a slipping magnetic clutch and utilizing the current generated in the armature to strengthen the field, so that the clutchis au tomatically compounded for varying loads.

' My-invention further consists in the combination of a unipolar machine'thus arranged wlth an alternating-current synchronous mo-' tor; the unipolar machine serving to transmit the power delivered by the alternating-cur rent motor, and being providedwith connec tions whereby the current induced in the unipolar machine serves to strengthen the field of the synchronous motor. Since the current induced inthe unipolar machine is .approximately proportional to the load, the synchroous motor may thus be com .ounded so as to operate with unity poweractor .underall' loads, or'with a leading current at full load, if desired. i I

My inven'tion further consists in providing a second unipolar machine supplied with current from..the"first,'and arranged to assist in driving the driven member. By means of this arrangement the current induced in-the be designed with very wardly extending pole-pieces.

unipolar machine is not all wasted in heat,

but a portion of it is transformed into useful work. By varying the relative field-strength of the two machines, the speed and torque ratios between the synchronous motor and the driven member may be varied.

In certain of its aspects my invention is not limited to the employment of a unipolar machine,/-but'instead a direct-current machine of the commutator type may be employed.

My'in-vention will best be understood by reference to the accompanying drawings, lIli which n Figure 1 shows an end elevation of a synchronous motor provided with power-trans mitting mechanism arranged in accordance with my invention; 2 shows a side elevation, partly in cross-section, of the same; Fig.

3 shows a detail cross-sectional view of the power-transmitting device; and Fig. 4 shows a modified arrangement of the apparatus.

In the drawings A represents the stationary armatu-re of an alternating-current synchronous motor carrying the usual armature coils a. r

F represents the field of the. synchronous motor, which is supported by and freelyiro tatable on the driven shaft. D. The field magnet F consists of twoparallel disks of magnetic material, each provided with in- The two disks are separate from each. other, except for the spacing bars E, shownin Fig. 1, i

which are made of non-magnetic..material,

a proper distance om each other.- Each diskcarries a magnetizing windingf, supplied through collector rings f, which extends cir cumferentially around the field magnet structure. Between the two, disks. which form. the field'magnet F is a disk C of con ducting material, and referably of iron or and which hold the olesxof the two disks at steel, keyed to the sha t D and forming the armature of a unipolar generator.

at the field magnet It will befseen t F not only forms a field magnet for the synchronous motor of the usual'type with projecting- Ioo poles of alternately op osite polarity, but

also forms a unipolar fie d for the conducting disk C. The single field winding f serves to produce the magnetization for both the syn chronous motor and unipolar generator.

The current induced in conducting disk C by rotation relative thereto of the field magnet F is led ofi by peripheral brushes 6, which are electrically connected to the poles of the field magnetF by conductors c, as shown in Figs. 1 and 2. The current collected by these brushes passes radially inward through the field magnet F and the brushes b, which bear on the inner portion of the conducting disk C andcomplete the armature circuit of the unipolar machine, which, as will be seen, is a short-circuit. With this arrangement it will be seen that any relative rotation of the field magnet F and the conducting disk C will induce in the unipolar machine a current which flows in the closed circuit ust described, and which tends to oppose the said relative motion,that is, the unipolar machine acts essentially as a slipping magnetic clutch between the field magnet F and the driven shaft D.

It will further be noticed that the conductors c, which convey the current from the peripheral brushes 5 to the field magnet, extend each in a circumferential direction, so that taken together they form a portion of a complete turn parallel to the field coils Consequently, the current'in these conductors assists the current in the field coils in mag netizing the machine, and since the load on the synchronous motor is substantially proportional to the current inducedin the uni polar generator, the magnetizing effect of this induced current maybe utilized, as above described, to compound the synchronous motor so as to secure operation at unity power-factor under all loads. The machine may even be over-compounded in this manner, if desired, so as to secure a leading current.

The operation of the power transmission mechanism, as thus far described, is as follows: at starting, the field coil f is denergized and the field magnet F is brought up to speed, running idle, as an induction motor secondary, by closing the armature circuit of the synchronous motor. When the field F is up to synchronism the circuit of the field Winding f would be closed, thereby simultaneously loading the field by inducing currents in the unipolar armature, and furnishing the excitation for locking the field magnet of the synchronous motor firmly in synchronism with the revolving field produced by the armature currents. The load on the synchronous motor is at all times approximately proportional to the current induced in the unipolar armature, and since this current in the conductors c strengthens the field of the synchronous motor, the synchronous motor maybe adjusted to operate at substantially unity ower-factor. To load on the unipolar mac ine is greatest at starting. Since at full speed the energy induced in the unipolar is small and since a machine of this type will stand excessive over-loads for a short period, this machine need not be of large capacity, as compared with the synchronous motor. As the driven shaft D speeds up, the voltage induced in the unipolar armature decreases until finally the driven shaft rotates at a speed less than the speed of the field magnet F byan amount the circuit of the field winding Since the disk C may be made so thin as to have very small inertia, the power required for frequent starting with high acceleration is comparatively small, and consequently my invention is especially applicable to driving loads requiring frequent and quick starting.

With the arrangement as thus far described, it is evident that the electric energy generated in the unipolar machine is eventually entirely dissipated in heat. In order to improve the efficiency of the device I propose to use the arrangement shown in Fig. 4. In this figure the conducting disk C is extended to form a sleeve keyed to the shaft carrying at its other end a second conducting disk C. The armature frame A is also extended so as to form a unipolar field structure surrounding the conducting disk C. A suitable magnetizing winding H-may be employed to produce the field for this unipolar machine. Brushes b at the periphery of the conducting disk C are connected by conductors c to brushes b bearing on the inner portion of the field magnet F. The current in, the leads from brushes b may be extended circumferentially in the manner heretofore described so as to supplement or to replace the magnetization by the winding H, and by adjusting the brush position, this series excitation may be varied.

The circuit of the unipolar machines is as follows from the conducting disk C outward through the branches b into the field magnet F radially inward through the field magnets, through the brushes b through the conductors c, to brushes If, radially inward through conducting disk C, and back to conducting disk C through the sleeve which joins the two disks. I have shown the field winding H in circuit with a source of separate excitation E, which may be the same source that furnishes the excitation for the synchronous motor. A variable resistance G is also placed in circuit with the field winding H. By means of this variable resistance the relative field-strengths of the two unipolar machines may be varied so as to vary the speed and torque ratios between the synchronous motor andthe driven shaft D. Or if the current in the brush leads is used for excitation, the same results may be obtained by shifting the IIC brushes so as to lengthen or shorten the leads.

, ture 0. As the driven shaft D speeds up, the

resistance would be cut into circuit'until the field cutting the disk C is reduced practically to zero and the armature C is conse quently practically short circuited. The driven shaft D then rotates substantially at the same speed as the field magnet F as in the arrangement of Fig. 2. It would even be possible to carry this operation further by reversing the terminals of the field coil II, so that the I armature C acts as a generator armature supplying current to the armature C and driving it as a motor. In this-way the driven shaft could be caused to operate at a higher speed than that of the field of the syn chronous motor. Over the entire range of operation, the energy developed in the uni polar armature C is converted into useful work instead of being wasted in heat, except when the armature C is short circuited at full speed, when the energy developed in the armature is small.

I have illustrated and described one par ticular arrangement of the unipolar machine and the synchronous motor, it is obvious that the constructions of both machinesmay be varied, as desired. Accordingly, I do not desire to. limit myself to the particular con struction and arrangement of parts here shown, but aim in the appended claims to cover all modifications which are within the scope of my invention.

, What I claim as new and desire to secure by Letters Patent of the United States, is:

1. In combination with a driving member and a driven member, a unipolar generator having its field magnet carried by one of said members and its armature carried by the other member, brushes carried by said field magnet for collecting the armature current and brush leads extending in a circumferen- 5 ,tial direction, whereby the current in said leads assists in magnetizing said field magnet.

2. In combination with a driving member anda driven member, a unipolar generator having its field magnet carriedby one of said members and its armature carried by the other member, current'oollecting means for transferring the armature current to the field magnet, and conductors in circuit with said collecting means eXtendmg 1n a circumferential direction. I

3. In combination with a driving member and a driven member, a unipolar generator having its field magnet carried by one of said members and its armature carried by the other member, a second unipolar machine comprising a field and armature one carried by one of said members and the other stationary, and connections for supplying to said second machine the current induced in the first unipolar machine.

4. In combination with a driving member and a driven member, a unipolar generator having its field magnet carried by one of said members and its armature carried by the other member, and connections whereby the induced armature current assists in magnetizing the field magnet.

5. In combination with a driving member and a driven member, arunipolar generator having its field magnet carried by one of said members and its armature carried by the other member, a second unipolar machine comprising a field and armature one carried by'one of said members and the other stationary, connections for supplying to said second machine the current induced in the fieldunipolar machine, and connections whereby said induced current assists in magnetizing one of said machines.

6. In combination with a driving member and a driven member, a unipolar generator having its field magnet carried by one of said members and its armature carried by the other member, a second unipolar machine comprising a field and armature one carried by one of said members and the other stationary, connections for supplying to said second machine the current induced in the first unipolar machine," and means for varying the relative field strengths of the two unipolar machines.

7. In combination with an alternatingcurrent synchronous motor, a driven member, a direct-current generator comprising 'field and armature, one carried by he rotaable member of said motor and the other by said driven member, and connections whereby the current induced in said generator strengthens the field of said motor.

8. In combination with an alternatingcurrent synchronous motor, a driven mem ber, a direct-current generator comprising field and armature one carried by the rotatable member of said motor and the other by said driven member, and a second direct-current machine supplied with current from the first direct-current machine and arranged to assist in driving said driven member.

9. In combination with an alternating current synchronous motor, a driven member, a direct-current generator comprising field and armature one carried by the rotatable member of said motor and the other by said driven member, a second direct-current machine supplied with current from the first direct-current machine and arranged to assist in driving said driven member, and connections whereby said current strengthens the field of said synchronous motor.

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10. In combination with an alternatingcurrent synchronous motor, a driven member, a direct-current generator comprising field and armature one carried by the rotatable member of said motor and the other by said driven member, a second direct-current machine supplied with current from the first. direct-current machine and arranged to assist in driving said driven member, and means for varying the relative field strengths of the two direct-current machines.

11'. In combination with an alternatingcurrent synchronous motor, a driven member, a unipolar generator comprising field and armature one carried by the rotatable member of said motor and the other by said driven member, and connections whereby the current induced in said unipolar generator strengthens the field of said synchronous motor.

12. In combination with an alternating current synchronous motor excited by a circumferentially extending field coil, a driven member, a unipolar generator comprising field and armature one carried by the rotatable member of said motor and the other by said driven member, current-collecting means for transferring the armature current of the unipolar generator to the field magnet, and conductors in circuit withsaid collecting means extending in a circumferential direction.

13. In combination with an alternatingcurrent synchronous motor, a driven member, a unipolar generator comprising field and armature one carried by the rotatable member of said motor and the other by said driven member, and a second unipolar machine supplied with current from the first unipolar machine and arranged to assist in driving said driven member.

14. In combination with an alternatingcurrent synchronous motor, a driven member, a unipolar generator comprising field and armature one carried by the rotatable member of saidmotor and the other by said driven member, a second unipolar machine supplied with current from the first unipolar machine and arranged to assist in driving said drlven member, and means .for varylng the relative field strengths of the two uni-- I polar machines.

15. In combination with a driven member, an alternating-current synchronous motor and a direct-current generator, one member of one machine being stationary and one member of the other machine being carried by ,said driven member an intermediate member comprising the other members of both machines and rotatable both with respect to the stationary member and to the driven member, and connections whereby the current induced in the direct-current generator strengthens the field of the synchronous motor.

16. In combination with a driven member, an alternating current synchronous motor and a direct-current generator, one member of one machine being stationary and one member of the other machine being carried by said driven member, an intermediate member comprising the other members of both machines and rotatable both with res ect to the stationary member and to the d iiven member, and a second direct-current machine supplied with current from the direct-current generator and arranged to assist in drivingsaid driven member.

17 In combination with a driven member, an alternating current synchronous motor and a direct-current generator, one member" of one machine being stationary and one member of the other machine being carried by said driven member, an intermediate member comprising the other members of both machines and rotatable both with respect to the stationary member and to the driven member, a second direct-current machine supplied with current from the direct current generator and arranged to assist in driving said driven member, and means for varying the relative field strengths of the two direct-current machines.

18. In combination with a driven member, an alternating-current synchronous motor and a unipolar generator, one member of one machine being stationary and one member of the other machine being carried by said driven member, and an intermediate member comprising the other members of both machines and rotatable both with respect to the stationary member andto the driven member.

19. In combination with a driven member, an alternating -current synchronous motor and a unipolar generator, one member of one machine being stationary and one member of the other machine being carried by said driven member, an intermediate member compri'sin the other, members of both machines an rotatable both with respect to the stationary member and to the driven member, and connections whereby the current induced in the unipolar generator strengthens the field of the synchronous motor.

20. In combination with a driven member, an alternatingcurrent synchronous motor and a unipolar generator, one member of one machine being stationary and one member of the other machine being carried by said driven member, an intermediate member comprisin the other members of both machines an rotatable both with respect to the stationary member and to the driven member, and a second unipolar machine supplied with current irom the unipolar generator and ber comprising the fields of both machines seams and a unipolar generator, one member of one machine being stationary and one member of the other machine being carried by said driven member, an intermediate member comprising the other members of both machines and rotatable both with respect to the stationary member and to the driven member, a second unipolar machine supplied with current from the unipolar generator and ar- 1 ranged to assist in driving the driven member, and means for varying the relative field strengths of the two unipolar machines.

22. In combination with an alternatingcurrent synchronous motor, a driven member, and a unipolar generator comprising field and armature, one carried by the rota table member of the synchronous motor and the other by said. driven member.

23.. In combination with a driven member, an alternating-current synchronous motor and a unipolar generator, the armature of one machine being stationary and the armature of the other machine being carried ,by said driven member, and an intermediate member comprising the fields of both machines rotatable with respect to both armatures.

24. In combination with a driven member, an alternating-current synchronous motor and a unipolar generator, the armature of one machine being stationary and the armature of the other machine being carried by said driven member, an intermediate memrotatable with respect to both armatures, and a single magnetizing Winding for both fields.

25. In combination with a driven member, an alternating-current synchronous motor and a unipolar generator, the armature of 1 one machine being stationary and the armature of the other machine being carried by said driven member, and an intermediate member comprising the fields of both machines rotatable with respect to both armatures, a single magnetizing winding for both fields, and connections whereby the current induced in the armature of said unipolar machine strengthens said fields.

26. In combination with a driven member, an alternating-current synchronous motor and a unipolar generator, the armature of one machine being stationary and the armature of the other machine being carried by said driven member, an intermediate member comprising the fields of both machines rotatable with respect to both armatures, and a circumferentially extending magnetizing coil for both fields.

27 In combination with a driven member, an alternating-current synchronous motor and a unipolar generator, the armature of one machine being stationary and the arma ture of the other machine being carried by said driven member, an intermediate member comprising the fields of both machines rotatable with respect to both armatures, a circumferentially extending magnetizing coil for both fields, means for collecting the current from the armature of said unipolar machine, and conductors in series with said collecting means extending in a circuml'erential direction.

In witness whereof I have hereunto set my hand this 29th day of November, 1905.

CAMPBELL MACMILLAN Witnesses BENJAMIN B. HULL, HELEN Unrorm. 

